1. Field of the Invention
The present invention relates to a semiconductor imaging device such as a CMOS sensor image.
2. Description of the Related Art
A semiconductor imaging device, especially a CMOS sensor, has been miniaturized in recent years, and generally uses copper (Cu) for interconnects with a pitch of 1.4 μm or smaller. In an imaging device using Cu interconnects, a cap layer composed of a Si3N4 film is formed on a Cu interconnect to prevent diffusion and oxidation of Cu. A SiN cap layer reduces light transmissivity. Therefore, a CiN cap layer on an optical path is removed from a pixel area.
A pixel area is surrounded by a dummy pixel area having substantially the same configuration as a pixel area, a black reference area for generating a black reference signal, an analog signal processing area, and a logic circuit area as a digital signal processing area. These areas are not exposed to light, and a Cu interconnect is present on a pixel. Therefore, a SiN cap layer is not removed (refer to Jpn. Pat. Appln. KOKAI Publication No. 2008-199059).
Semiconductor processing includes heat treatment so-called sintering, in which a dangling bond generated in a gate oxide film as a non-coupling means is terminated by hydrogen. However, as a SiN cap layer hardly transmits hydrogen, the amount of hydrogen applied to a substrate during sintering is different in a pixel area not having a SiN cap layer, a dummy pixel area having a SiN cap layer, a black reference area, and a logic circuit area. In other words, the amount of hydrogen is smaller in a dummy pixel area, black reference area, and logic circuit area than that in a pixel area, and the dangling bond is not sufficiently terminated in some locations in these areas. Thus, a transistor leakage current increases in a dummy pixel area, black reference area, and logic circuit area. Especially, at a dark period, the characteristic of a pixel area becomes different from those of a dummy pixel area, black reference area, analog signal processing area, and logic circuit area. Therefore, a semiconductor imaging device, in which semiconductor elements in a pixel area and other areas can be set to the same characteristics, is demanded.